Loans Held for Sale (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jul. 31, 2012 First Niagara [Member]	Jun. 30, 2012 First Niagara [Member]	Dec. 31, 2011 First Niagara [Member]
Loans Held for Sale (Textual) [Abstract]
Loan receivable held for sale for retail branch							$ 531	$ 2,500
Commercial loan receivable held for sale for retail branches	115		115		521		115	521
Residential Mortgage Loan Receivable Held for Sale for Retail Branches	279		279		1,400		279	1,400
Credit card receivable held for sale for retail branches	94		94		416		94	416
Other consumer loan receivable held for sale for retail branches	43		43		161		43	161
Fair value of commercial loans held for sale	411		411		377
Fair value of subprime mortgage residential loans held for sale						170		181
Loans Held for Sale (Additional Textual) [Abstract]
Residential mortgage loans held for sale include subprime residential mortgage loans at fair value	164		164		181
Subprime residential mortgage loans sold			4	129
cumulative fair value adjustment on loans held for sale	228		228		251
Fair value of commercial real estate loans held for sale	313		313		55
Fair value of commercial loans held for sale	411		411		377
Gain on trading related revenue associated with this economic hedging program		1	4
Loss on trading related revenue associated with this economic hedging program	$ 3			$ 11